<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>数组扁平化</title>
</head>
<body>
    
</body>
<script>
    let arr = [1, [2, 3], [4, 5, 6]]

    function fn(arr){
        let newArr = []
        for(let i = 0; i<arr.length; i++){
            if(Array.isArray(arr[i])){
                newArr = newArr.concat(fn(arr[i]))
            } else {
                newArr.push(arr[i])
            }
        }
        return newArr
    }

    console.log(fn(arr))


    // es6 flat，有些浏览器不兼容
    console.log(arr.flat(3))
</script>
</html>